Sound recording device



Oct. 19, 1937. M. VON ARDENNE SOUND RECORDING DEVICE Filed July 6, 1935 .9 .41 151517 5- figgg M m m m m M m m w m. m m m &

INVENTOR. Manfred 1/027 flraenn ATTORNEY.

Patented Oct. 19, 1937 sire 'r orries SOUND RECORDING DEVICE York Application July 6, 1935, Serial No. 30,204 in Germany March 12, 1935 9 Claims.

This invention relates to novel means and a method for recording sound or other physical quantities photographically, and more particularly to the production of sound records of the variable amplitude or variable width type as distinguished from the variable density type record known in the art. In the former, the modulation of the light is obtained by a record or sound track on the photographic emulsion of uni- 10 form density but varying in width, while in the latter case the modulation of the light is obtained by a record or sound track of substantially constant width but varying emulsion density according to the variations of the sound waves.

Sound records of the variable width or variable amplitude type are superior to records of the variable density type in several respects, primarily with regard to absence of distortion caused by and during the copying process of sound films from the original or master film recorded by the sound camera.

It is an object of the present invention to provide a simple and eflicient recording device for producing variable amplitude sound records, more particularly records of the double or multiple amplitude type characterized by high fidelity and efliciency as compared to similar recording devices and methods heretofore known in the art.

A more specific object of the invention is the 30 provision of a simple and efficient recording tube constructed and operating in accordance with the principles of the cathode ray oscillograph and adapted for producing photographic sound records in accordance with the variable amplitude or variable width method, more particularly sound records of the multiple amplitude type.

As pointed out before, the variable amplitude type record for sound recording and reproducing, especially for talking picture use, is superior in 40 many respects to variable density records due to reduced distortion of the sound variations. By using a double or multiple amplitude record, especially in connection with the novel system and method described by the invention, the disadvan- 45 tages inherent in the previous variable amplitude recording systems are substantially overcome.

With the above objects in View, the invention relates to a novel type of cathode ray oscillograph tube for sound recording and adapted to overcome 50 the defects and disadvantages of devices of this type heretofore known in the art. The latter are due primarily to a lack of definition or sharpness of the fluorescent recording spot or line, to distortions incident to the control of the recording 55 cathode ray and similar causes well known. In

addition, the recording device as described by the invention has the further advantage of a substantially increased light output resulting in an increased eflicienoy as compared to similar devices known in the prior art. ;5

The invention has further objects and aspects which will appear hereafter from the following detailed description taken with reference to the accompanying drawing wherein I have illustrated one form of a recording tube structure and sys- 1Q tem of sound recording constructed in accordance with the principles of the invention.

In the drawing:

Fig. 1 illustrates diagrammatically the production of a multiple type. variable amplitude record 15 upon the fluorescent screen of a cathode ray recording tube in accordance with the invention; and

Figs. 2 and 3 illustrate in horizontal and vertical sectional views, respectively, a recording 20 tube and associated sound recording system.

Similar reference numerals identify similar parts in the different views of the drawing.

The new recording device according to the invention substantially comprises a means such as an electron gun, associated with an electric'lens system for producing an extremely sharp luminous line upon the fluorescent screen of a cathode ray device and means for variably deflecting the luminous recording line at right angle to its length in accordance with the variations of the sound to be recorded. In order to secure a rec- 0rd of variable amplitude upon the photographic film exposed to the light of the fluorescent screen of the tube, I furthermore provide an opaque screen or mask arranged close to the fluorescent screen and having a marginal curve of suitable shape, such as a serrated shape in such a manner as to obtain a fluorescent line broken into sections of variable length resulting in a multiple variable amplitude record on the recording film.

Referring more particularly to Fig. 1 of the drawing, I have shown an arrangement of this type in diagrammatic form. Item I represents the fluorescent screen of a cathode ray oscillograph impinged upon by a cathode ray of narrow linear cross section causing a sharply defined linear luminous line upon the screen as shown at 3. Item 2 represents an opaque blind or mask having one edge thereof formed of toothed or serrated shape with teeth shown at 2. In this manner, the recording line 3 is broken and divided into a plurality of sections as shown. As is seen, by deflecting the recording line in a di-' rection at right angle to its length as indicated by the'arrows a-a' in the drawing, the width or amplitude of the individual linear elements be tween the teeth 2' of the screen 2 are varied'accordingly, resultingin a multiple variable area' sound record on a film upon which the sound signals are recorded photographically. i

As is understood, the luminous recording line should normally be adjusted in such a manner that the total light flux produced and collected;

for instance by means of a suitable optical lens system corresponds to thedesired operating point light modulation curve of the recording device' to suit any special requirements.

In order to obtain a multiple type variable width record upon the photographic film by means of the device as described, it is only necessary to'produce a reduced image of the interrupted or broken fluorescent line upon the photographic film by means of a suitable optical system. In order to insure a sound record free from distortion and undesired wobbling frequencies especially when recording sound waves of high frequencies and large amplitude, the optical system for producing the light from the fluorescent screen upon the photographic film should be constructed in accordance with a further feature of the invention in such a manner that the variations of the position of the fluorescent line during the control operation do not affect the position of the image'upon the photographic film. This requirement may be fulfilled by using an opticalsystem in the form of a cylindrical lens oriented in such a manner as to function as a collecting lens only in the direction at right angle to the movement of the recording film. 'Such a lens associated with a suitable light slit element is adapted to produce a multiple linear and stationary image upon the photographic film of varying area depending upon the length of the separate interrupted luminous line sections on the fluorescent screen of the tube. In order to secure the required width of the' line record, it is only necessary, as pointed out, toprovide a light slit of narrow width in the focal. plane. of the lens designed and related to the speed of the film such as to reproduce the highest frequency component of the sound which it is desired to record and reproduce photographically.

Referring to Figs. 2 and 3, these show a struc tural embodiment of a recording tube and syspassed through the stem or press of the tube and serving for applying the heating current to the cathode in a known manner to cause adequate electron emission; Item 9 represents a concentration electrode negatively biased relative to the cathode and being of cylindrical shape mounted concentrically with the cathode 8. This electrode, which is connected to an outside lead 9,.is provided with a narrow horizontal slot shown at H] for securing an electron pencil of narrow linear cross section impinged upon a further concentric electrode ll provided with a horizontal slot 12 being in register with the slot ll! of the electrode 9. The electrode I l is suitably biased positively with regard to the cathode through a terminal lead connection shown at H and serves as a first acceleration electrode for the cathode ray pencil. Items I3 and [5 represent a pair of further cylindrical electrodes also concentrically mounted with the remaining electrodes and provided with horizontal slots l4 and IS in register with the slots l0 and I2. These electrodes which are also suitably positively biased such as through terminal leads connections I3 and I5, serve to provide a cylindrical electron lens system for producing a sharply focused image of the cathode ray pencil of narrowlinear cross section upon the fluorescent screen 6 at the opposite end of the tube, resulting in a well defined luminous recording line." I have furthermore shown a serrated opaque screen 2 or mask applied to the outside of the tube 4 opposite the fluorescent screen 6 and serving for the purpose as described and explained hereinbefore. In order to deflect the cathode ray pencil to produce a variable area multiple record as described, I have furthermore shown a pair of parallel deflecting plates l1 and I8 preferably of arcuate shape arranged concentrically to the other electrodes of the tube and connected to terminal leads I1 and l 8f for applying the controlling or deflecting potentials sup-' plied from a suitable input device such as a microphone circuit through a transformer 23, 24 or any other suitable coupling device. An image of the' broken fluorescent line obtained from the tube is projected upon the photographic film 22 by means of a cylindrical lens 20 which in the position shown collects only light rays of angular spread in a plane at right angle to the movement of the recording film 22; that is, in the example shown at Fig. 2, within or parallel to the plane of the drawing. Item 2| represents a light slit element to limit the width of the light record to a value required for recording and reproducing the highest desired sound frequency components. I have furthermore shown a normal collecting lens I!) arranged between the screen 6 and the cylindrical lens 20 and serving for collecting and utilizing substantially all the light emitted from the fluorescent screen. The focal length of this additional lens should be such, as shown irf Fig. 2, that together with the cylindrical lens 2!] a sharp image is produced upon the photographic film.

The cylindrical lens 20 has no refracting power in the direction of the movement of the photographic film. This would normally result in an incomplete collection of thefluorescent light. By a proper design of the focal length of the cylindrical lens 20 however, it is possible to increase its collecting power to such an extent as to obtain sufficient luminosity at the recording light slit. Experiments have furthermore shown that even when providing a normal collecting lens in the path of the light rays from the fluorescent screen to the recording film, the required effect of the cylindrical lens is practically insured in such a manner that substantially no variations of the position of fluorescent line but only varia-' tions of its amplitude or amplitudes aflect the photographic film.

As is obvious, the luminous recording line provided in accordance with the invention may be secured by any well known system differing from the arrangement as disclosed in the drawing. Thus for instance such a luminous line may be obtained by a periodic deflection of a concentrated cathode ray by means of a high frequency sweep potential in connection with a suitable electron lens system or similar concentrating system, resulting in a sharp and Well defined luminous line on the fluorescent screen. A construction of a tube of the type as disclosed and described in more detail in my copending application, Ser. No. 26,625, filed June 14, 1935, entitled Recording device, for producing a sharp luminescent line has been found to give satisfactory results in a recording system of the specific type as described by the present invention on account of its simple construction and ease of operation and its optical efiiciency as well as of lack of distortion. In a tube of this construction as described above and in the mentioned copending application, the electrons emitted from the cathode are accelerated in a fan-shaped beam resulting in a highly uniform luminescent line on the recording screen and in turn in high fidelity and lack of distortion of the sound record.

As is understood, the deflection of the cathode ray may be carried out in any other convenient manner differing from the arrangement as shown by means of the are shaped deflecting plates ll and I8. Thus, for instance, magnetic deflecting coils of known type may be provided for controlling the position of the fluorescent recording line on the luminous screen. When using electric deflection as shown in the drawing by means of defleeting plates, it has been found advisable to connect the deflecting plates separately to the outside of the tube and to apply the controlling potential variations in a symmetrical manner with regard to ground or the negative terminal of the system. This is shown in Fig. 3 wherein the deflecting parts I! and I B'are connected to the opposite ends of the secondary winding 24 of an input transformer having a primary 23 for applying the recording current such as a current supplied from a microphone circuit with the center point of the secondary winding connected to the final acceleration electrode I5 usually maintained at negative or cathode potential in accordance with the common practice and operation of cathode ray tubes.

As will be evident from the above description, the invention is not limited to the specific embodiments presented herein for illustration and. the underlying principle and inventive concept and susceptible of various modifications differing from the specific disclosure herein presented and coming within the broad scope and spirit of the invention as defined in the appended claims.

I claim:

1. In a recording apparatus for producing a variable area sound track, a cathode ray tube comprising means for producing a flat cathode ray beam, a fluorescent screen and an electron lens system for focusing said beam upon said screen to produce a luminous line thereon, means for variably deflecting said beam so as to move said line in a direction transverse to its length in accordance with sound variations to be recorded, a photographic film, means for projecting an image of said luminous line upon said film,

said film moving in a .direction transverse to the image of said line projected thereon, and a mask arranged between said screen and said film adapted to intercept the light beam projected from said luminous line upon said film to vary the length of the image of said line upon the film in accordance with the deflection of said cathode ray beam.

2. In a sound recording apparatus, a discharge device comprising means for producing a flat cathode ray beam therein, a fluorescent screen impinged by said beam to produce a luminous line thereon, means for variably deflecting said beam so as to move said line in a direction transverse to its length in accordance with sound Variations to be recorded, a photo-sensitive member moving in a direction transverse to said line, an .optical lens arranged between said screen and said photo-sensitive member and adapted to collect only the light rays of angular spread in a plane at right angle to the movement of said photo-sensitive member to produce an image of said line upon said photo-sensitive member, a light slit element in front of said photo-sensitive member, and a light stop having a saw-tooth shaped outline arranged between said screen and said lens and adapted to break up said image into a plurality of lengths each varying in accordance with the deflection of said beam.

3. In a sound recording apparatus, a discharge device comprising means for producing a flat cathode ray beam therein, a fluorescent screen impinged by said beam to produce a luminous line thereon, means for variably deflecting said beam so as to move said line in a direction transverse to its length in accordance with sound variations to be recorded, a continuously moving photographic film, a cylindrical lens oriented so as to collect only light rays of angular spread in a plane at right angle to the movement of said film to produce an image of said line upon said film, a light slit element arranged in front of said film, and a saw-tooth shaped light stop arranged between said screen and said lens and adapted to break up said image into a plurality of adjacent lengths each varying in accordance with the deflection of said beam;

4. In a recording apparatus for simultaneously producing a plurality of adjacent identical variable area optical record tracks, a discharge device comprising means for producing a flat cathode ray beam therein, a fluorescent screen impinged by said beam to produce a luminous line thereon, means for deflecting said beam so as to move said line in a direction substantially transverse to its length in accordance with variations of a magnitude to be recorded, a photo-sensitive member, means for projecting an optical image of said line upon said photo-sensitive member, said photo-sensitive member moving in a direction transverse to the image of said line thereon, and a saw-tooth shaped light stop arranged between said screen and said photo-sensitive member adapted to break up said image into a plurality of adjacent sections each having a length varying in accordance with the deflection of said beam.

5. In a recording apparatus for simultaneously producing a plurality of adjacent identical variable area sound tracks, a discharge device comprising means for producing a flat cathode ray beam, a fluorescent screen impinged by said beam to produce a luminous line thereon, means for deflecting said beam so as to move said line in a direction substantially transverse to its length in accordance with variations of sound to be recorded, a photo-sensitive member, means for proverse to the linear image thereon, and a sawtooth shaped light stop arranged between said screen and said photo-sensitive member adapted to break up the image of said line on said photosensitive member into a plurality of adjacent sections each having a length varying in accordance with the deflection of said beam.

6. In a recording apparatus for simultaneously producing a plurality of adjacent identical variable area sound tracks, a cathode ray tube comprising means for producing a flat cathode ray beam therein, a fluorescent screen on the inside wall of said tube impinged by said beam to produce a luminous line thereon, means for deflecting said beam to move said line in a direction transverse to its length in accordance with variations of sounds to be recorded, a photo-sensitive record carrier, means for projecting an optical image of said luminous line upon said record carrier, said record carriermoving in a direction transverse to the image of the line thereon, and a saw-tooth shaped mask applied to the outside wall of said tube opposite said screen and adapted to break up the image on said photo-sensitive member into a plurality of adjacent sections each having a length varying in accordance with the deflection of said beam.

7. In a recording apparatus for simultaneously producing a plurality of adjacent identical varibeam, a fluorescent screen, an electron lens system for focusing said cathode beam upon said fluorescent screen to produce a luminous line thereon, means for variably deflecting said cathode ray beam in a direction transverse to its cross-sectional length in accordance with variations of sound to be recorded so as to move said 7 line in a direction transverse to its length, a. photographic fllm, means for projecting an optical image of said luminous line upon said photographic film, said photographic film moving in a direction transverse to the image of the line proj ected thereon, and a saw-tooth shaped light stop arranged between said screen and said photographic 'film adapted tobreak up the image upon said photographic film into a plurality of adjacent sections each having a length varying in accordance with the deflection of said beam.

8. In an apparatus as claimed, in claim 1 in which said first mentioned means is comprised of a source of electrons, a, first arcuate electrode having a slot therein,and having its concave side directed towards said source, and a further arcuate acceleration electrode having a slot substantially parallel to said first slot. 7

9. In an apparatus as claimed in'claim 1 first means comprising a source of, electrons, an arcuate concentration electrode having a slot therein and having its concave side directed towards said source, an arcuate acceleration electrode having a slot substantially parallel to said first slot, and said deflecting means comprising a pair of arcuate deflecting plates disposed at opposite sides of said electron beam.

I MANFRED VON ARDENNE. 

